Bit rate control is one of important techniques in video encoding and plays an important role in applications in the fields of video storage and video transmission. For a limited bit rate, especially a video online transmission with a low bit rate, bit rate control is particularly important and decides the quality of the video encoding directly. In the existing bit rate control methods for video encoding, bit rate control is usually accurate to macroblock level, so as to make the output bit rate of the encoder more accurate. However, conventional bit rate control methods of this kind have high computational complexity and large amount of calculation. Moreover, at the same time when increasing the control accuracy, the non-uniform image quality in space for the same image is resulted due to the non-uniform bit rate allocation. Especially in the condition of wireless/low band-width, such negative effects will be amplified, and the condition of non-uniform image quality resulted by local over-quantification in the image will be very obvious, which may damage the subjective effect of the image greatly.